The present invention is directed to the use of salts of sulfocarboxylic acid esters as catalysts.
The sodium salts of sulfocarboxylic acid esters are well known and have been used frequently in coatings applications. Perhaps best known is their use as surfactants and to this end, a multitude of materials are commericially available. However, these materials are becoming increasingly diversified and other applications are common. For example, U.S. 4,169,825 to Yapp et al is directed to a high solids polyester-containing coating composition which utilizes a sodium sulfated dioctyl succinate as a curing catalyst. These compositions are cured by heating at high temperatures, i.e., up to about 400.degree. F. U.S. Pat. No. 4,294,738 is directed to water-based coating compositions prepared from low molecular weight addition copolymers of polar vinyl monomers. These compositions contain sodium di-2-ethylhexylsulfosuccinate as a miscibilizing agent. The presence in coating compositions of these sodium salts is not without attendant disadvantages. For example, when utilized as curing catalysts, these materials do not cure as well at lower temperatures. This is readily demonstrated by evaluating hardness and solvent resistance of the cured films. Moreover, the appearance of films containing such sodium salts is often unsatisfactory when a high gloss is desired. Since the sodium salts are generally not very soluble in the composition, they tend to migrate and concentrate at the film surface thereby dulling the appearance. Therefore, a sulfocarboxylic acid ester curing catalyst is desired which not only cures well at low temperatures but which also results in a good film appearance and properties.